Developing liquid feed device for wet process electrophotographic apparatus

ABSTRACT

A developing liquid feed device to be used in a wet process electrophotographic apparatus for feeding a developing liquid having a toner concentration higher than that of the developing solution in the main developing chamber, comprising a developing liquid feed storage tank having a normally closed valve therein which valve is opened by appropriate means when the tank is mounted upon the main developing chamber permitting the developing liquid therein to be metered into the main developing solution. A premix chamber is floated in the main developing solution beneath the valve in the storage tank to receive the developing liquid passing therethrough. This premix chamber is provided with means for exerting a buoyant force sufficient to overcome the head of the developing liquid and thus maintains the uppermost edge of the premix chamber above the level of the developing solution. When the developing solution is at a predetermined level, the developing liquid in the premix chamber closes off the valve so that there is no metering of the developing liquid from the storage tank, but when the solution drops below the predetermined level, the concurrent dropping of the premix chamber opens the valve, permitting developing liquid to pass through the premix chamber into the main developing chamber until the solution is again raised to the predetermined level.

Unite States Patent Inventor 8 Suzuki Primary Examiner-M. Cary NelsonYokmamav Japan Assistant Examiner David R. Matthews PP 31,629AttorneysHenry T. Burke, Robert Scobey, Robert S. [22] P"- 1970 Dunham,P. E. Henninger, Lester W. Clark, Gerald W. [45] Patented Nov. 30, 1971Griffin, Thomas F. Moran, R. Bradlee Boal, Christopher C. 1 AsslsneeRiwh Dunham and Thomas P. Dowd Tokyo, Japan [32] Priority Apr. 25, 1969[33] Japan ABSTRACT: A developing liquid feed device to be used in a[31] 44/32510 wet process electrophotographic apparatus for feeding adeveloping liquid having a toner concentration higher than that of thedeveloping solution in the main developing chamber, comprising adeveloping liquid feed storage tank having a normally closed valvetherein which valve is opened [54] DEVELOPING LIQUID FEED DEVICE FOR WETby appropriate means when the tank is mounted upon the PROCESSELECTROPHOTOGRAPHIC mam develop|ng chamber permitt ng the developmgliquld APPARATUS therem to be metered into the mam developing solution.A 4Claims2brawlng Figan premix chamber s floated In the mam developingsolut on beneath the valve In the storage tank to receive the developing[52] U.S. Cl 137/454, quid passing h r thmu h. This premix chamber isprovided 137/575- 137/581 with means for exerting a buoyant forcesufficient to over- [51] Int. CL G05d 9/00 come the head fth developingquid and thus maintains the [50] Field of Search 137/386, uppermast edgef the premix chamber above the |eve| f he 409, 4301 454, 58]; developingsolution. When the developing solution is at a 251/251;95/89; 101/48,364 determined level, the developing liquid in the premix ReferencesCited chamber closes off the valve so that there is no metering of thedeveloping liquid from the storage tank, but when the solution UNITEDSTATES PATENTS drops below the predetermined level, the concurrentdropping 2,279,166 4/ 1942 Hodil et a1. 137/386 of the premix chamberopens the valve, permitting developing 2,360,894 10/1944 Ryan 251/251 Xliquid to pass through the premix chamber into the main 3,145,653 8/1964Lake 137/454 X developing chamber until the solution is again raised tothe 3,491,675 1/1970 Gold 137/414X predetermined level.

9 26 I8 I00 25 L S i 2 7 [3b =fi=? T 2O 3 '0 1-H? a 7 l6 15b 0 7 4 I Ilb |4l 1 la 60 lo DEVELOPING LIQUID FEED DEVICE FOR WET PROCESSELECTROPIIOTOGRAPI'IIC APPARATUS BACKGROUND OF THE INVENTION The presentinvention relates to a developing liquid feed device for a wet processelectrophotographic apparatus.

The developing liquid for the wet process electrophotography consists ofa carrier having a high electric resistance and the toner or finelydivided resinous powder such as carbon black. Only when the tonerconcentration in the developing liquid is maintained at a predeterminedlevel, a latent electrostatic image is developed into a visible image ofbetter quality.

When a large number of copies are developed by the same developingliquid, the toner and the carrier are consumed as they are adhered tothe copies or sensitized members so that the toner concentration as wellas the quantity of the developing liquid are decreased. The tonerconcentration must be maintained at a predetennined degree by supplyingthe toner itself or the new developing liquid. In this case, it will bevery advantageous to supply the developing liquid in the developingliquid chamber with the developing liquid feed whose concentration ispreviously adjusted so as to maintain the toner concentration in thedeveloping liquid in the developing liquid chamber when the quantity ofthe developing liquid is decreased less than a predetermined value. Thetoner concentration Dp (gJt) in the developing liquid feed is given byDp= [DV- Dn (V- Vrl)]/Vn where D (g./t) desired toner concentration inthe developing liquid in the developing liquid chamber:

Dn(g./L) toner concentration of the developing liquid after a number ofn copies or sensitized members have been developed;

Vn (L) quantity of the developing liquid required for the development ofa number of n copies or sensitized members; and

V(L) quantity of the developing liquid which must remain in thedeveloping liquid for a desired image quality.

Dn and Vn may be detennined empirically and statistically depending uponthe sizes of the copies or sensitized members, the density of black areato white area of a pattern to be copied, etc. V may be determineddepending upon a design capacity of a photocopying machine. Thus, Dp maybe determined from the above relation. The concentration D has abolerance so that the developing liquid feed having a concentration Dp(g./:.) is supplied into the developing chamber, the developing liquidin the chamber may be maintained at a predetermined level.

In order to supply the developing liquid feed into the developing liquidchamber, a feed valve which is opened when the liquid level in thedeveloping liquid chamber falls below a predetermined level is generallyused. However, when the feed valve is simply opened in this manner intothe developing liquid, the developing liquid feed may be automaticallysupplied depending upon the liquid level in the developing liquidchamber, but the developing liquid in a storage tank is in communicationwith the developing liquid in the chamber so that the toner in thedeveloping liquid feed is deposited or dispersed into the developingliquid, thereby reducing the toner concentration in the liquid.Therefore, even when the developing liquid feed is fed into thedeveloping liquid a predetermined toner concentration in the developingliquid cannot be maintained because the toner concentration of theliquid is less than a desired level.

SUMMARY OF THE INVENTION It is therefore the broad object of the presentinvention to provide an improved developing liquid feed device for usein a wet process electrophotography which can completely separate thedeveloping liquid feed from the developing liquid to which is added thefeed, except the time when the feed must be supplied to the developingliquid, thereby preventing undesired drop of toner concentration of thedeveloping liquid feed and maintaining the toner concentration of thedeveloping liquid in the developing liquid chamber always at a desiredlevel.

Another object of the present invention is to provide an improveddeveloping liquid feed device which can automatically feed thedeveloping liquid feed having a toner concentration higher than that ofthe developing liquid when the liquid level in the developing liquidchamber falls below a predetermined level, thereby maintaining alwaysthe toner concentration of the developing liquid in the chamber at apredetermined level.

A further object of the present invention is to provide an improveddeveloping liquid feed device simple in construction yet highly reliableand dependable in operation at less cost.

To attain the above and other ends, the present invention provides animproved developing liquid feed device comprising a developing liquidfeed tank in which is tored the developing liquid feed whose tonerconcentration is so adjusted that when it is added to the developingliquid, the latters toner concentration may be maintained at a desiredlevel, said storage tank having a valve of the type which is opened andclosed depending upon the level of the developing liquid means fornormally opening said valve when said storage tank is mounted upon adeveloping liquid chamber; a premix developing liquid chamber withinsaid developing liquid chamber in opposed relation with said valve forvertical movement in response to the liquid level within said developingliquid chamber; and means for exerting the buoyancy on said premixdeveloping liquid chamber so as to position the uppermost peripheraledge of said premix developing liquid chamber at a level substantiallyequal to or higher than said liquid level in said developing liquidchamber; whereby when said premix developing liquid chamber lowers inresponse to the falling of said liquid level in said developing liquidchamber, said storage tank is communicated with said developing liquidchamber through said premix developing liquid chamber.

According to one embodiment of the present invention, the premixdeveloping liquid chamber is movably fixed to the side wall of thedeveloping liquid chamber through a laterally extending arm, butaccording to another embodiment of the present invention, the premixdeveloping liquid chamber is floating in the developing liquid in thedeveloping liquid chamber and its vertical movement is guided by a rodextending from the bottom of the developing liquid chamber and beingfitted loosely into a guide fixed to the bottom of the developing liquidchamber so that the lateral deviation of the intermediate chamber isprevented when it moves vertically.

The developing liquid feed device in accordance with the presentinvention can supply the developing liquid feed in an accurate quantitydepending upon the liquid level or quantity of the developing liquid inthe developing liquid chamber so that the quantity and concentration ofthe developing liquid within the chamber can be always maintained atdesired levels. When the desired quantity of the developing liquid is inthe chamber, the developing liquid can be completely separated from thedeveloping liquid feed in the storage tank so that the dilution of thedeveloping liquid feed due to the deposition and dispersion of the tonercan be completely prevented, even though the conventional valve which isopened or closed in response to the liquid level in the developingsolution chamber is employed. The device of the present invention issimple in construction requiring no special valve.

The above and other objects, features and advantages of the presentinvention will become more apparent from the description of thefollowing embodiments thereof with reference to the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of oneembodiment of a developing liquid feed device in accordance with thepresent invention; and

FIG. 2 is a fragmentary sectional view of another embodiment of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig. 1, referencenumeral 1 designates a developing liquid chamber; 2, a developingliquid; and 3, a passageway of a copy paper. Middle plates 4 are firmlyfixed to stepped portions la and lb of the chamber 1. The passageway 3of the copy paper is defined by a guide plate 5 supported by the middleplates 4, another guide plate 6 spaced upwardly of the lower guide plate5, a pair of feed rollers 7 and 8 pressed against each other and a pairof discharge rollers 9 and 10 which serve also as a pair of squeezerollers. The copy paper is inserted into the nip between the feedrollers 7 and 8 in the direction indicated by the arrow. The upper andlower guide plates 6 and 5 are bowed or concaved downwardly so that thecopy paper may be immersed into the developing liquid 2 and constructedof metal plates having a plurality of elongated slits 5a and 6aextending in the longitudinal direction. A developing liquid mixingframe 1! in the chamber 1 is pivotably fixed to the lower end of adepending arm 13a of a rocking member 13 which is pivotably fixed to asidewall by a pin 12. An uprightly bent edge 13b of the other arm of therocking member 13 is normally pressed by a spring 14 against aneccentric cam 10a carried by the shaft of the roller l0. It is thereforereadily seen that the rocking member 13 is caused to rock upon rotationof the roller 10 which drives the eccentric cam 100 which in turn drivesthe uprightly bent edge 13b, so that the mixing frame 1 1 isreciprocated from left to right and from right to left in Fig. 1.Therefore, the developing liquid 11 is suitably agitated so that thedeposition of the toner can be prevented and the new developing liquidmay be always applied to the copy paper being developed.

Upwardly of the upper guide plate 6 is disposed a premix developingliquid chamber 15 having a buoy 15a such as cork attached to the bottom.A free end of an arm 15b extending from the premix developing liquidchamber 15 is pivotably fixed by a pin 16 to the sidewall 1a of thechamber 11. A developing liquid feed tank 18 is disposed above theintermediate chamber 15. The tank 18 is provided with a developingliquid feed valve 17 which is opened and closed depending upon the levelof the developing liquid in the chamber 15. When the tank 18 is notmounted in the photocopying machine a valve 17a is normally is firmlypressed against a valve seat 17d by a spring 17c fitted over a valvestem [7b, so that the developing liquid 18a within the tank 18 iscompletely sealed from the exterior. When the tank 18 is mounted asshown in Fig. l, the valve stem 17b is caused to move upwardly againstthe spring 170 by a stationary valve receiving member 19 having itssupporting arms 19a securely fixed to the sidewall la of the chamber 1so as to be interposed between the valve 17 and the intermediate chamber15. Therefore, the outlet or valve 17 of the tank 18 is normally opened.As described hereinbefore, the concentration of the developing liquidfeed 20 in the tank 18 is maintained at a desired value so that when itis supplied to the chamber 1, the developing liquid in the chamber maybe always maintained at a predetermined value.

The feed tank 18 is supported resiliently by retaining members 22 and 23which in turn are securely fixed to resilient members. A felt 25attached to the side surface of a tank-supporting frame 24 is pressed bya spring 26 against the roller 9 so that the toner and the like attachedto the roller 9 may be removed therefrom.

Next the mode of operation will be described. It should be noted thatthe intermediate chamber 15 and the valve-receiving member 19 areconstructed independently. Since the intermediate chamber 15 is appliedwith the buoyancy by the buoy 150, so that the peripheral side edges ofthe intermediate chamber 15 is positioned at a level equal to or higherthan the level of the developing liquid 2 within the chamber 1, thevalve 17 is normally opened. When the level of the developing liquid 2in the chamber 1 rises or falls, the intermediate chamber 15 also risesor lowers about the pin 16 so that the supply of the developing liquidfeed 2a in the tank 18 is started or stopped in response to the movementof the intermediate chamber 15. More specifically, when the developingliquid 2 is consumed so that the intermediate chamber 15 is moveddownwardly in the direction indicated by the arrow b, the developingliquid feed 2a in the tank 18 is supplied first into the intermediatechamber 15 and then into the chamber 1. When the level of the developingsolution 2 reaches a predetermined level, the intermediate chamber 15rises so that the developing liquid 2 in the intermediate chamber 15closes the opening of the valve 17, thereby stopping the supply of thedeveloping liquid feed 20 in the tank 18 into the intermediate chamber15. It is seen that the sidewalls of the intermediate chamber 15 serveto the developing liquid 2 from the developing liquid feed 2a. Theheight D from the level of the developing liquid 2 to the peripheralside edge of the intermediate chamber l5 may be suitably designed sothat the timing of the supply of the developing liquid feed 2a from thetank 18 to the intermediate chamber 15 may be suitably selected.

Next the second embodiment of the present invention will be describedwith reference to Fig. 2. A guide rod llSb extending from the bottom ofthe intermediate chamber "5 having the buoy 1150 is loosely fitted intoa guide member 116 which is securely fixed in turn to the chamber 1 sothat the vertical movement of the intennediate chamber is controlled. Asin the case of the first embodiment described hereinabove, when theintermediate chamber 115 is lowered in the direction indicated by thearrow 0 with the fall of the level of the developing liquid 2, thedeveloping solution feed 2a in the tank 18 is supplied into the chamber1 through the intermediate chamber I15. When the level of the developingliquid 2 rises as the feed 2a is supplied, the opening of the valve 17is closed by the developing liquid 2. The side wall of the intermediatechamber 115 serves to separate the developing liquid 2 from thedeveloping liquid feed 2a when the developing liquid 2 reaches apredetermined level. Further description of the second embodiment willnot be required since the arrangements and functions of other componentsare similar to those of the first embodiment.

The present invention has been described so far with particularreference to the preferred illustrative embodiments thereof, but it willbe understood that variations and modifications can be effected withoutdeparting the true spirit of the present invention as describedhereinabove and as defined in the appended claims.

I claim:

1. A developing liquid feed device for wet process electrophotographycomprising a developing liquid feed tank containing a developing liquidfeed whose toner concentration is so previously adjusted that when it isadded to a developing liquid in a developing chamber, a desired tonerconcentration of the developing liquid may be always maintained, saidtank having a valve of the type which is normally closed means foropening said valve when said tank is mounted upon said developing liquidchamber;

a premix developing liquid chamber within said developing liquid chamberin opposed relation with said valve for vertical movement in response tothe liquid-level in said developing liquid chamber; and

means for exerting on said intermediate chamber the buoyancy so as toposition the uppermost peripheral edge of said premix developing liquidchamber at a level substantially equal to or higher than the liquidlevel in said developing liquid chamber,

whereby when said intermediate chamber is lowered in response to thefalling of the liquid level in said developing liquid chamber said tankis intercommunicated with said developing liquid chamber through saidintermediate chamber, thereby feeding the developing liquid feed to saiddeveloping liquid.

2. A developing liquid feed device as specified in claim I wherein saidpremix developing liquid chamber has an arm whose one end is securelyfixed to said intermediate chamber and whose the other end is pivotablyfixed to the chamber, said tank having a valve therein for meteringsidewall of said developing liquid chamber, whereby said said secondsupply of developing liquid to said developing intermediate chamber maymove along a predetermined chamber; path when the liquid level in saiddeveloping liquid c. apremix chamber floated in the first supply ofdeveloping chamber varies. 5 liquid in said developing chamber incooperating relation 3. A developing liquid feed device as specified inclaim 1 with said valve; and wherein said intermediate developing liquidchamber hasa d. means for exerting a buoyant force on said premix rodextending downwardly from the bottom of said inter- Chamber sufiicientto maintain the uppermost edge of mediate chamber and fitted into guidemeans securely Said p i h fn above h le el f h first supply of fixed tothe bottom of said developing liquid chamber, 10 defelopingliquld inSaid q p f chamber, such thereby preventing the lateral deviation ofsaid inter- Said Valve Closed y f P Chamber when said mediate chamber whn it i moved i ll first supply of developing llquld IS above apredetermined 4. Apparatus for wet process electrophotography,comprislevel Sald developing chamber and said Valve Opens icommunicating said second supply of developing liquid to a a developingchamber containing a first Supp|y of 15 said developing chamber throughsaid premix chamber developing liquid; when said first supply ofdeveloping liquid drops below b. a developing liquid feed tankcontaining a second supply Predetermmed levelof developing liquid andmounted on said developing

2. A developing liquid feed device as specified in claim 1 wherein saidpremix developing liquid chamber has an arm whose one end is securelyfixed to said intermediate chamber and whose the other end is pivotablyfixed to the sidewall of said developing liquid chamber, whereby saidintermediate chamber may move along a predetermined path when the liquidlevel in said developing liquid chamber varies.
 3. A developing liquidfeed device as specified in claim 1 wherein said intermediate developingliquid chamber has a rod extending downwardly from the bottom of saidintermediate chamber and fitted into guide means securely fixed to thebottom of said developing liquid chamber, thereby preventing the lateraldeviation of said intermediate chamber when it is moved vertically. 4.Apparatus for wet process electrophotography, comprising a. a developingchamber containing a first supply of developing liquid; b. a developingliquid feed tank containing a second supply of developing liquid andmounted on said developing chamber, said tank having a valve therein formetering said second supply of developing liquid to said developingchamber; c. a premix chamber floated in the first supply of developingliquid in said developing chamber in cooperating relation with saidvalve; and d. means for exerting a buoyant force on said premix chambersufficient to maintain the uppermost edge of said premix chamber abovethe level of the first supply of developing liquid in said developingchamber, such that said valve is closed by said premix chamber when saidfirst supply of developing liquid is above a predetermined level in saiddeveloping chamber and said valve opens communicating said second supplyof developing liquid to said developing chamber through said premixchamber when said first supply of developing liquid drops below saidpredetermined level.